remove DEFAULT_DEVICE again

The deprecation warning didn't work as expected.
It always shows on import.

This reverts 070ca1d0c0c26e61819acca57bc58ac4ca44cfcf.
doc: discid.rst -> api.rst

Previous links don't break, since discid is still the module name, which
still links to the api.
/discid/#module-discid is a highly redundant link though.
That's why I changed to /api
Merge branch 'revert_1.0.1'

see pull-request #35